Anybody know what this oil pan fits?

[Dynaflash8]

I have a NOS oil pan that makes no sense. It is exactly like my 1939 Special oil pan, except the drain hole is in the back, instead of being on the side. I have talked to a number of long-time Buick mechanics/restorers and none of them have ever seen a prewar straight 8 oil pan with the drain plug on the back (well, bottom back). Is there anybody on line who knows what this oil pan is meant to fit. The next question, of course, is, if I every use it, will the oil drain be interferred with by something else, like say the clutch cover? Years ago I got this oil pan from a Buick dealerl when I was selling Buick parts.